checkpatch: add --strict preference for p = kmalloc(sizeof(*p)...

Add another test for memory allocation style to follow
Documentation/CodingStyle:

		Chapter 14: Allocating memory

The preferred form for passing a size of a struct is the following:

	p = kmalloc(sizeof(*p), ...);
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -3507,6 +3507,14 @@ sub process {
 			     "unnecessary cast may hide bugs, see http://c-faq.com/malloc/mallocnocast.html\n" . $herecurr);
 		}
 
+# alloc style
+# p = alloc(sizeof(struct foo), ...) should be p = alloc(sizeof(*p), ...)
+		if ($^V && $^V ge 5.10.0 &&
+		    $line =~ /\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*([kv][mz]alloc(?:_node)?)\s*\(\s*(sizeof\s*\(\s*struct\s+$Lval\s*\))/) {
+			CHK("ALLOC_SIZEOF_STRUCT",
+			    "Prefer $3(sizeof(*$1)...) over $3($4...)\n" . $herecurr);
+		}
+
 # check for krealloc arg reuse
 		if ($^V && $^V ge 5.10.0 &&
 		    $line =~ /\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*krealloc\s*\(\s*\1\s*,/) {